Using developit/unfetch as the Fetch API polyfill (#1278)

lib/router/router.js

@@ -10,7 +10,7 @@ import { _notifyBuildIdMismatch } from './'
 
 // Add "fetch" polyfill for older browsers
 if (typeof window !== 'undefined') {
-  require('whatwg-fetch')
+  require('unfetch/polyfill')
 }
 
 export default class Router extends EventEmitter {

package.json

@@ -79,12 +79,12 @@
     "source-map-support": "0.4.11",
     "strip-ansi": "3.0.1",
     "styled-jsx": "0.5.7",
+    "unfetch": "2.0.0",
     "url": "0.11.0",
     "uuid": "3.0.1",
     "webpack": "2.2.1",
     "webpack-dev-middleware": "1.10.1",
     "webpack-hot-middleware": "2.17.1",
-    "whatwg-fetch": "2.0.2",
     "write-file-webpack-plugin": "3.4.2"
   },
   "devDependencies": {